The recovery of the location of a mobile device, such as a cellular telephone or a smart phone, is the basis for a wide range of Location-Based-Services (LBS). A Location Based Service is an information service, accessible to mobile devices through the cellular network utilizing the geographical position of the mobile device. Location based services can be used in a variety of contexts, such as health, work, personal, and entertainment by identifying the location of an individual or object using the position of the mobile device and providing the individual with information regarding various service providers in the same location as the individual. LBS can include sending advertising directed at customers based on their location, personalized weather services, locations of restaurants, gas stations, other businesses, and comparable services.
Various techniques may be utilized in order to determine the location of a mobile device, including network based cell tower triangulation, Global Positioning System (GPS), peer-based systems (e.g. Bluetooth based short range systems), and Wireless Local Area Networks (WLAN). Network-based techniques, such as cellular triangulation, utilize the service provider's network infrastructure and temporal delay of tower signals from nearby cell towers' receptions to identify the location of a mobile device within a “cell.” This method is the most common as it can be implemented cost effectively and non-intrusively while the mobile device is not actively in use by the user. However, the accuracy of this technique is relatively low due to its dependence on the concentration of base station cells, achieving an accuracy of a few tenths of meters in urban areas, but as poor as hundreds of meters in suburban areas and rural zones. Accuracy may also vary due to obstacles such as large buildings and weather conditions.
Using WLANs may apply a similar triangulation method with the WLAN signal origination spot as the basis for the triangulation cell, or more commonly the location can be estimated by sensing a single WLAN source, as the WLAN range is typically limited. This method may be more useful in urban areas, where the relatively large number of WLAN spots may generate smaller cells relative to cell towers and increase positional accuracies. However, WLAN spots must be mapped relative to the world, and their use is dependent on a comprehensive database of WLAN access points. WLAN points maybe very dynamic, and may be added, removed, turned on and off quite frequently. Their accuracy may also be reduced due to obstacles and weather. Another approach using GPS is the most accurate method of locating a mobile device to within 10-30 meters. However, this approach requires substantial computation power and is energy expensive, which may rapidly deplete battery power on a mobile device. As a result, GPS based location determination is commonly used for short intervals or in specific navigation tasks, and is not continuously activated on most mobile devices. GPS is also difficult to be sensed in indoor environments.